Financial and Clinical Toxicity of Empiric Vancomycin for Intra-Abdominal Infections: A Cohort Study

Background: Vancomycin for intra-abdominal infections (IAI) should be reserved for healthcare-acquired infections, history of multiple interventions, or methicillin-resistant Staphylococcus aureus (MRSA). The MRSA incidence is low; however, fear of missing MRSA leads to overutilization. Methods: This single-center retrospective cohort study evaluated the cost and risks of empiric vancomycin for IAI. The primary objective was to determine the incidence of MRSA-positive culture and surveillance testing. Secondary outcomes included acute kidney injury (AKI) incidence, progression to dialysis, direct costs of vancomycin overutilization, length of stay, and 30-day mortality. Results: A total of 1,045 patients with IAI were identified and 491 (47%) received at least one dose of vancomycin. Thirty patients (2.9%) grew MRSA. Of those who grew MRSA, 21 (70%) were MRSA positive on the surveillance multi-drug resistance (MDR) culture or by polymerase chain reaction during hospitalization. There were no deaths within the MRSA group. AKI developed in 351 (33.6%) patients during their hospitalization, with 49.6% occurring within 48 hours of vancomycin administration. Of the 65 patients (6.9%) who required dialysis, 27 patients (42%) received vancomycin. The cost of unnecessary doses equated to $21,655 and $188,643.84 for vancomycin levels. Conclusion: Given the low MRSA culture incidence, it is reasonable to avoid vancomycin as empiric treatment for those being admitted for IAI alone to reduce the risk of AKI and reduce healthcare costs. Vancomycin should be limited mainly to those with a positive MRSA culture with consideration of vancomycin in those at highest MRSA risk such as a history of MRSA or known MRSA colonization.